Description:
<jats:title>Abstract</jats:title><jats:p>Cold ecosystems in regions of high‐latitude and altitude with vast stores of soil organic carbon suffer strong freeze‐thaw cycles, which can greatly affect soil CO<jats:sub>2</jats:sub> release. However, on the Tibetan Plateau, where altitude is >4,000 m, it remains unknown how freeze‐thaw processes regulate CO<jats:sub>2</jats:sub> production across the soil profile. In this study, we used the gradient method to explore impacts of freeze‐thaw processes on depthwise soil CO<jats:sub>2</jats:sub> production in an alpine steppe. We found almost all soil CO<jats:sub>2</jats:sub> was produced in the root‐zone layer (<30 cm), while the root‐free layer (>30 cm) frequently alternated between being a source and sink of CO<jats:sub>2</jats:sub> and thus acted largely as a buffer. The surface layer (0–15 cm) and subsurface layer (15–30 cm) had a similar CO<jats:sub>2</jats:sub> production rate in the thawed period. However, during the freezing‐frozen‐thawing period, the subsurface layer consistently functioned as a weak CO<jats:sub>2</jats:sub> source, although parts were trapped in frozen soil, resulting in a weaker CO<jats:sub>2</jats:sub> sink in the surface layer. Soil CO<jats:sub>2</jats:sub> production in subsurface layer is thus more sensitive to temperature variability compared with surface layer. Furthermore, our results suggest water content plays a more important role than temperature in regulating soil CO<jats:sub>2</jats:sub> production. For the first time, our data set reveals the vertical production of CO<jats:sub>2</jats:sub> within the seasonally frozen soils on the Tibetan Plateau, which will benefit understanding of belowground carbon processes and modeling of soil CO<jats:sub>2</jats:sub> release in the region.</jats:p>